The present invention relates to releasably attaching an object to a bone in a living patient, and relates particularly to a device for fastening an object such as a component of a computerized surgical navigation system stably to a large bone such as a femur.
In surgical procedures involving articulated skeletal bone joints, such as knee replacement procedures, it is often helpful to use computer-aided navigation, based on infrared or electromagnetic imaging systems, to locate bones or parts of bones correctly with respect to each other during the procedure. In order to establish and monitor the position of a large bone as a reference for such computer-aided navigation, a reference device must be securely and stably, but removably, mounted on the large bone.
Attachment of objects to bones has been addressed by the prior art, as disclosed, for example, by Glossop U.S. Pat. No. 6,203,543 and Sasso U.S. Patent Application Publication No. US2005/0119566.
In attaching some known devices to a bone as a mounting support for a navigation system reference target or beacon, a screw is inserted transversely through a large bone such as the femur, using a hole drilled entirely through the thickness of the bone. In order to be secure the screw must be long enough to extend beyond a shoulder or other depth-limiting stop far enough to extend into the cortex of the bone on the far side. At the same time, however, the screw should not be so long as to extend unnecessarily beyond the far side of the bone when the shoulder or other stop is seated on the near side of the bone. Accordingly, such a device must be available in various different lengths for use with bones of different sizes. While an estimate can be initially made of the size of a bone, time may be wasted if a mounting device of the wrong size is chosen initially and must be replaced.
Adjustment of some previously available devices to securely support an object such as a part of a navigation system has required separate operations of first drilling and thereafter tapping screw holes in bones, taking more time than is desired during a surgical procedure.
In other devices for anchoring an object to a bone a bone engaging part of the device must be rotated as it is moved through soft tissue surrounding the bone in order to bring that part of the device into engagement against the bone. This rotary motion during movement through the soft tissue causes undesired trauma to the soft tissue and may delay healing in that area.
Adjusting a mounting fastening device to attach it securely to a bone has thus been a difficult and inexact procedure in the past.
What is desired, then, is a device and a method for its use to attach an object securely to a large bone, and to accomplish such attachment without taking an undue amount of time, and with a predictable result, so as to achieve a secure attachment in a device which is readily removable when its presence is no longer required.